There is always a need for stronger and harder alloys to improve the performance and lifetime of structures and platforms. Engineers are looking for high strength materials to improve performance and safety, while maintaining low weight requirements. Strength limitations directly affect how industrial parts are used. Engineers are actively looking for alloys with material properties sufficient for manufacturing and use, while providing fatigue, fracture, and corrosion resistance, while maintaining or improving mechanical properties.
Fatigue and fracture strengths of machinery parts, non-moving parts such as gun barrels, and weldments can be improved by generating high compressive strengths on their surface. The benefit is that the compressive stresses must be overcome before tension strains can be produced leading to crack initiation and extension. A number of known methods are used industrially for enhancing the surface strength profile. This includes the application of plastic stresses imparted using large rolling machines, carbonizing, shot peening, and explosive detonation.
Many industrial parts, which cannot be otherwise produced by casting, rolling or forging can be fabricated using powder metallurgy techniques. The parts, such as gears, shafts, and brackets etc., are compacted and the powder with matrix portions are bonded together using hot isostatic pressing (HIP), along with follow-on heat application. Dynamically compressing parts under high dynamic loading is a useful process.
Another known technique for treating the surfaces of industrial parts to improve fatigue and fracture properties is shot peening. This technique enables a rise in the hardness of a surface layer of a work piece and introduction of compressive residual stress into the surface layer. This technique is widely used in the industrial fields of automobiles, aircrafts, etc.
Yet another known technique is laser shock hardening. This involves irradiating the surface of a solid material, such as a metal or a ceramic, with pulsed laser beam through a liquid to adjust surface of internal characteristics of the material, such as structure, hardness and residual stress.
Generally speaking, laser shock hardening has a higher effect than shot peening and in addition has various excellent advantages that shot peening does not have, such as capability of contactless operation, no involvement of reaction force and capability of precise control of laser irradiation conditions and laser irradiation sites. Even with all these known techniques, it is still desired to have a method and an apparatus to improve the ability to strengthen and to make more compact, the surface of industrial parts. Such a method may also be used to supplement other forms of surface hardening, such as carburizing, nitriding and cyaniding.